Ernst Fetterlein

Who was Ernst Fetterlein?

Ernst Constantin Fetterlein was a Russian cryptographer who later defected to Britain.

Fetterlein was born in St Petersburg, the son of Karl Fedorovich Fetterlein, a German-language tutor, and Olga Fetterlein, née Meier. He studied a variety of eastern languages at the University of St Petersburg, graduating in 1894. On 25 November 1896 he joined the Ministry of Foreign Affairs. He eventually became the chief cryptologist for the Tsar of Russia, holding the rank of "General-Admiral," an honorary title in Tsarist Russia. During World War I, he was known for a time as Ernst Popov as his German-derived name could have drawn unwanted attention. Amongst others, he solved German, Austrian and British codes.

Upon the Russian Revolution of 1917, he fled to Western Europe with his wife on board a Swedish ship, narrowly evading capture. He contacted the British and French intelligence organisations, offering to work for whoever would pay him the most, which was apparently the British, as he was recruited to Room 40 in June 1918 to work on Georgian, Austrian and Bolshevik codes.